Type about:preferences#search<enter> in the address box. You can select any search engine to be your default from here.

You can also remove any engine from here.

If you want to add a search engine, check this link: https://mycroftproject.com/

Check your Google settings. Also Firefox Settings > General > Language.

Hi, is this problem in Firefox on your iPhone? Your question ended up under Firefox for desktop (Windows/Mac/Linux) so if a moderator needs to move it to iOS, let us know.